Calculate the $pH$ after the addition of the following volumes of $0\mathrm{.}2M$ NaOH to $30mL$ of $0\mathrm{.}2$ M H$2$X $($H$2$X is a diprotic acid

with $K{a}_1=2\mathrm{.}1{10}^{-5},K{a}_2=4\mathrm{.}4{10}^{-9}).$

a$)5\mathrm{.}0mL$ of NaOH

b$)30\mathrm{.}0mL$ of NaOH

c$)50\mathrm{.}0mL$ of NaOH

d$)70\mathrm{.}0mL$ of NaOH